There are the Download Over The Air standardized by the OMA (Open Mobile Alliance) and the OTA (Over The Air) of MIDP (Mobile Information Device Profile), which define the scheme for a client terminal, for instance a mobile phone, to download contents from a contents server.
Especially, these standards define that the client terminal receives a Download Descriptor (hereinafter “DD”), which describes attribution information of the contents, before downloading contents, and the client terminal downloads the contents from the contents server based upon the URI (Uniform Resource Identifier) contained in the DD.
The contents to be downloaded from the contents sever are a movie, music, and a game program, etc.
By the way, in order to avoid the load of unnecessary fee collection or a network, it is desirable that the client terminal does not download the same contents as contents which the client has already downloaded from the contents server.
For example, Japanese Patent Disclosure (Kokai) No. 2003-216430 discloses a system where upgrade of unnecessary software is not performed. In this system, which consists of a client terminal and a server, the client terminal stores the operating frequency of each software, and client terminal requests the server to upgrade only software with high operating frequency for reducing useless access to the server.
However, if there are two or more contents from which only voice information differs, the above-mentioned scheme cannot solve the problem. That is, although it is desirable to download only the voice information in Japanese if the client terminal has already downloaded the content with image information and voice information in English, a scheme for downloading only voice information in Japanese is not provided.